<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8" />
  <title>15_姓名案例</title>
  <!-- 引入Vue -->
  <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
  <!-- 准备好一个容器-->
  <div id="demo">
    姓:<input type="text" v-model="firstName"><br>
    名:<input type="text" v-model="lastName"><br>
    姓名:<span>{{fullname}}</span>

  </div>
</body>

<script type="text/javascript">
  //阻止 vue 在启动时生成生产提示。
  Vue.config.productionTip = false;
  let vm = new Vue({
    el: '#demo',
    data: {
      firstName: 'zhang',
      lastName: 'san',
      fullname: ''
    },
    // 计算属性
    // computed: {
    //   getFullNames: {
    //     get() {
    //       return this.firstName.slice(0, 1).toUpperCase() + this.firstName.slice(1) + '-' + this.lastName
    //     },
    //   }fa9968
    // },
    watch: {
      firstName: {
        immediate: true,
        handler(value) {
          setTimeout(() => {
            this.fullname = value + '-' + this.lastName
          }, 1000)
          console.log(value);
        }
      },
      lastName(value) {
        setTimeout(() => {
          this.fullname = this.firstName + '-' + value
        }, 1000);

      }
    }
  })
  console.log(vm);
</script>

</html>